Shinsu Reactant (신수 반응액) also known as Clicker (똑딱이) is an item that visualizes user's shinsu quality. It was created by Po Bidau Gustang during the Great Journey.
When you press the button in the center, the liquid inside reacts to your qualities and attributes and shows you the shape of your shinsu quality.
In the Hidden Floor, Khun Eduan gave it to Baam to help him visualize his shinsu quality, when he had trouble figuring it out. The item was used by Twenty-Fifth Baam, Rak and Khun Aguero Agnis. Presumably used by other characters such as Endorsi who were also present.